#include <bits/extc++.h>
using namespace std;
// using namespace __gnu_pbds;
// #include <boost/multiprecision/cpp_int.hpp>
// using Bint = boost::multiprecision::cpp_int;
// #include <atcoder/all>
// using namespace atcoder;
// https://atcoder.github.io/ac-library/production/document_ja/
typedef long long int ll;
typedef long double ld;
constexpr ll mod = 1e9+7;
constexpr ll INF = 9'223'372'036'854'775'807/10;
#define rep(i,n) for (ll i = 0; i < ll(n); ++i)
#define Rep(i,a,n) for (ll i = (a); i < ll(n); ++i)
#define All(a) (a).begin(),(a).end()
#define Pi acos(-1)
using V = vector<ll>;
using P = pair<ll,ll>;
vector<ll> dx = {1, 0, -1, 0, 1, 1, -1, -1};
vector<ll> dy = {0, 1, 0, -1, 1, -1, 1, -1};
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
struct Edge{ll to, cost;};
using Graph = vector<vector<Edge>>;
struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    cout << setprecision(15) << fixed;
  }
} iosetup;
void print(vector<string> &v) {
  for (string s : v) {
    cout << s << '\n';
  }
}
template<typename T>
void print(vector<T> &v, int w = 0) {
  for (int i = 0; i < (int)v.size(); i++) {
    cout << right << setw(w) << v[i] << " \n"[i == (int)v.size() - 1];
  }
}
template<typename T>
void print(vector<vector<T>> &v, int w = 0) {
  for (int i = 0; i < (int)v.size(); i++) {
    print(v[i], w);
  }
}
template<typename T>
void print(const T& arg) {
  cout << arg << '\n';
}
template<typename T, typename... Args>
void print(const T& arg, const Args&... args) {
  cout << arg << ' ';
  print(args...);
}

ll bit_to_ll(string s) {
  ll res = 0;
  for (char c : s) {
    res <<= 1;
    res += c - '0';
  }
  return res;
}

int main() {
  string s, t;
  cin >> s >> t;
  ll a = bit_to_ll(s);
  ll b = bit_to_ll(t);
  cout << (a^b) << '\n';
}